How to fix CSV mojibake (garbled text): Excel, UTF-8, and Shift_JIS

A CSV is just a text file, but it does not always clearly carry which character encoding it was written in. When the side that wrote the file and the side that opens it assume different encodings, the same bytes get read as different characters — and you get garbled text.

For many languages the two usual suspects are UTF-8 and a legacy local encoding (for Japanese, Shift_JIS / cp932). Open a UTF-8 CSV in a tool that assumes the legacy encoding (or vice versa) and only the non-ASCII text breaks. ASCII looks fine while accented or non-Latin characters garble — that is the telltale sign.

If non-ASCII text is garbled while numbers, ASCII text, and column positions still look right, the encoding is the problem. Reopen the file as UTF-8, Shift_JIS, or its actual source encoding instead of editing the broken characters by hand.

If the text is readable but every value lands in one column, the delimiter is the problem instead. Check whether the file uses commas, semicolons, or tabs. If columns start shifting partway down, inspect embedded commas, line breaks, and double quotes before changing the encoding.

A UTF-8 CSV without a BOM can open as garbled text when Excel, its version, or the Windows locale assumes a different encoding. That is an interpretation mismatch rather than a corrupted file.

Microsoft recommends either saving the UTF-8 CSV with a BOM or importing it through Data → From Text/CSV. Adding the BOM is convenient when recipients need to double-click the file without repeating import settings.

To fix it locally, open the CSV in an editor like Notepad or VS Code and re-save it with an explicit encoding. If you want Excel to open it cleanly by double-click, saving as UTF-8 with a BOM is the safest choice and works in most environments.

If instead you are feeding a legacy system that expects Shift_JIS, you need to export in that encoding. Confirm which one the recipient expects first, and you save yourself several rounds of re-saving.

Beyond encoding, CSVs love to drift columns. When a cell contains a comma or a line break that is not properly wrapped in quotes ("), the column count stops matching. Address fields and free-text notes are common offenders.

Sometimes the delimiter is a tab or semicolon rather than a comma. If everything lands in one column, or columns shift badly, suspect the delimiter and quoting — not just the encoding.

Filewisp's Fix CSV Encoding tool reads UTF-8, Shift_JIS, and UTF-16 LE or BE, then exports UTF-8 with or without a BOM. A five-row preview shows the decoded text and column count before download, so you can catch a wrong choice immediately.

Auto mode detects UTF-8 and UTF-16 BOMs and otherwise starts with UTF-8. If the preview is still garbled, explicitly choose Shift_JIS. If the preview remains a single column, switch to the CSV Delimiter Converter because encoding conversion will not change separators.

Rather than hand-patching a broken CSV, it is often faster to route it through another format. Convert CSV to JSON to inspect the structure, or convert to Parquet for a data platform so the types and encoding are pinned down.

Our CSV to JSON and CSV to Parquet tools run in the browser, so even CSVs with customer or internal data convert without leaving your device — handy when you just want to see what is inside.

CSV garbling is almost always a UTF-8 vs Shift_JIS mismatch. Match the encoding the recipient expects, and for Excel re-save as UTF-8 with a BOM. If columns drift, check the delimiter and quoting too.

Fix CSV Encoding, CSV Delimiter Converter, CSV ⇄ JSON, and CSV ⇄ Parquet all run in-browser on Filewisp, so you can choose the fix that matches the symptom without uploading the data.